I do not know how to import the "deck" array into my perfectShuffle method/class (idk wtf is the difference)

This Does NOT compile because my perfectShuffle cant find ''deck''

I'm pretty sure you're gonna look at my code and be like 'wtf do u even know what you're doing?' well no I dont know what i'm doing but ive gotten super far with not knowing what im doing by creating a deck array of every card in a deck of cards.

Im struggling to find the flow from class/method/object/instance watever and how they interact.